1. Field of the Invention
The present invention relates to a direct methanol fuel cell (DMFC), and more particularly, to a method for fabricating a releasable bipolar of the DMFC.
2. Description of the Prior Art
A fuel cell is an electrochemical cell in which a free energy change resulting from a fuel oxidation reaction is converted into electrical energy. Fuel cells utilizing methanol as fuel are typically called Direct Methanol Fuel Cells (DMFCs), which generate electricity by combining gaseous or aqueous methanol with air. DMFC technology has become widely accepted as a viable fuel cell technology that offers itself to many application fields such as electronic apparatuses, vehicles, military equipment, the aerospace industry, and so on.
DMFCs, like ordinary batteries, provide DC electricity from two electrochemical reactions. These reactions occur at electrodes (or poles) to which reactants are continuously fed. The negative electrode (anode) is maintained by supplying methanol, whereas the positive electrode (cathode) is maintained by the supply of air. When providing current, methanol is electrochemically oxidized at the anode electrocatalyst to produce electrons, which travel through the external circuit to the cathode electrocatalyst where they are consumed together with oxygen in a reduction reaction. The circuit is maintained within the cell by the conduction of protons in the electrolyte. One molecule of methanol (CH3OH) and one molecule of water (H2O) together store six atoms of hydrogen. When fed as a mixture into a DMFC, they react to generate one molecule of CO2, 6 protons (H+), and 6 electrons to generate a flow of electric current. The protons and electrons generated by methanol and water react with oxygen to generate water.
FIG. 1 and FIG. 2 illustrate a conventional DMFC 10, wherein FIG. 1 is a plain view of a conventional DMFC 10 and FIG. 2 is a cross-sectional view of the conventional DMFC 10 along line I-I of FIG. 1. As shown in FIG. 1 and FIG. 2, the conventional DMFC 10 comprises a bipolar plate assembly 12 and a fuel container 14. The bipolar plate assembly 12 comprises an upper frame 51, lower frame 52, a cathode wire lath 121, a plurality of bended bipolar wire laths 122, 123, 124, 125, an anode wire lath 126, and membrane electrode assemblies (MEAs) 131, 132, 133, 134, 135 interposed between corresponding wire laths.
However, the above-described conventional DMFC 10 has several drawbacks. First, the bipolar plate assembly 12 is too thick and thus too unwieldy to carry. Furthermore, as mentioned, the cost of producing the conventional DMFC 10 is high since the cathode wire lath 121, bended bipolar wire laths 122, 123, 124, 125, and the anode wire lath 126 are titanium meshes treated by gold plating. In addition, the throughput of the conventional DMFC 10 is low because the bipolar wire laths 122, 123, 124, 125 are bended manually before mounting on the upper and lower frames. In light of the above, there is a need to provide a thin, inexpensive, and highly integrated DMFC that is capable of achieving the scale of mass production.